Sonographic characteristics and clinical characteristics combined with nomogram for predicting the aggressiveness of papillary thyroid carcinoma coexisted with Hashimoto’s thyroiditis

Highlights • HT played a protective role in PTC.• Blood flow was a risk factor of aggressiveness in PTC.• A nomogram for predicting the aggressiveness of PTC.


Introduction
Evidence level: This article's evidence level is 3. Level 3 evidence is derived from non-randomized, controlled clinical trials.In this study, patients who receive an intervention are compared to a control group.Authors may detect a statistically significant and clinically relevant outcome.
Papillary Thyroid Carcinoma (PTC) accounts for the highest proportion (more than 90%) of all thyroid carcinomas. 1 Most PTCs have an indolent disease course with a low mortality rate and a favorable prognosis even after low-intensity treatment. 2In consequence, a wide range of options are employed for disease management, from active surveillance to surgical treatment and subsequent radioactive iodine ablation. 3Hence the stratification of PTC patients by risk of aggressiveness has been the main clinical issue.Several clinicopathologic characteristics have been currently recognized as risk factors of unfavorable prognosis, such as older age, large primary tumor size, Extrathyroidal Extension (ETE), Lymph Node Metastasis (LNM), and Distant Metastasis (DM). 4 According to ATA guideline, aggressive treatment is recommended for PTC patients with these risk factors.Otherwise, low-intensity treatment may be sufficient. 3evertheless, these managements are all based on clinicopathologic analysis, resulting in excessive unnecessary surgeries.Preoperative multifaceted accurate evaluation must be carried out by identification of specific biomarkers, invasive sonographic features and aggressive clinical characteristics. 5ashimoto's Thyroiditis (HT) occupies the major proportion of autoimmune thyroid disorders, causing chronic inflammation of the thyroid tissue. 5The coexistence rate of PTC combined with HT reported in epidemiologic studies is increasing, ranging from 5% to 85%. 6,7Although the existence of association between HT and PTC development and progression has been accepted, there always been controversial.Due to the less invasive disease and the lower recurrence rate, coexistent HT is widely believed playing a protective role in PTC. 8 Lymphocyte infiltration caused by HT and facilitating antitumor immunity maybe connected with this function, which makes the association rational. 9owever, few studies regarding the association of HT with PTC in aggressiveness by sonographic characteristics of PTC with the presence of coexistent HT.This study was aimed at assessing and determining the clinical characteristics and sonographic characteristics for predicting the aggressiveness of PTC coexisted with HT, by univariate analysis, multivariate analysis and nomogram.

Patients
This study was conducted according to Declaration of Helsinki and approved by the Institutional Ethical Committee.Three hundred and seventy-three consecutive patients (275 females and 98 males; age range: 18---80 y; mean age: 45.04 ± 12.27 y) were enrolled from January 1 st , 2017 to December 31 st , 2020 in this study (Fig. 1).In addition, we collected 111 patients (86 females and 25 males; age range: 21---68 y; mean age: 42.76 ± 11.24 y) as validation cohort from January 1 st to August 31 st , 2021.All patients received lobectomy or total thyroidectomy for PTC with/without coexistent HT at our hospital.Informed consent forms for general use of clinical information in future studies were obtained at the time of operation.

Image analysis
All patients were detected by conventional Ultrasound (US) and color Doppler US.Sonographic characteristics include tumor size >1.0 cm, marked hypoechoic, taller than wide, distance to capsular ≤0 cm, microcalcification, irregular margin and multifocality (Fig. 2A---B, D---E).Blood flow of nodules was classified into the following 3 levels: Grade 0, no blood flow in the nodule; Grade I, the nodules show a small amount of blood flow, only a few spots of blood flow or one long vessel penetrating into the nodule (more than half of the maximum diameter of the nodule); and Grade II, there is abundant blood flow inside the nodule, with 5 or more punctate blood flow or 2 long vessels. 10These sonographic characteristics were all confirmed by two experienced US experts using MyLab Twice (Esaote, Italy) with the probe LA523.

Histopathology
Standard pathologic diagnosis followed the World Health Organization criteria.Coexistent HT, primary tumor size, ETE, gross ETE, and LNM of thyroid were confirmed by two pathologists with at least 5 years of working experience (Fig. 2C---F).HT was diagnosed on pathological examination of surgical specimen to avoid the confounding effects of autoimmune antibodies. 11Absent LNM was defined, if one patient who did not undergo lateral compartment dissection with his negative result of US examination for lymph nodes.In this study, PTC was defined as aggressiveness, when ETE, gross ETE, or LNM was showed in pathological histology result.

Statistical analysis
Mean ± Standard Deviation (SD) indicated quantitative data.Student's t-test, Pearson 2 test or Fisher's exact test were used for clinicopathologic characteristics and sonographic characteristics compared across groups.Multivariate logistic regression analysis was used in order to identify risk factors for PTC with/without coexistent HT and to identify risk factors for aggressiveness in PTC.The nomogram was established for predicting the aggressiveness of PTC in patients.The diagnostic accuracy of prediction of aggressiveness was calculated with Receiver Operating Characteristic (ROC) analysis.The discriminative ability of the predictive nomogram was assessed by Harrell's Concordance Index (C-index).The calibration curve was used to determine the prediction compliance.The Decision Curve Analysis (DCA) was used to evaluate the clinical application value of the model; p-value < 0.05 was considered statistically significant.All statistical analyses were performed using the SPSS 26.0 statistical package (SPSS, Inc., Chicago, IL, USA), and R language software and R Studio.
A relevant predictive nomogram was established with integrated clinical (age ≥55 years; gender; HT) and sono-   graphic factors (tumor size >1.0 cm; multifocality; distance to capsular ≤0 cm; blood flow) to assist in preoperative predicting aggressiveness of PTC (Fig. 3).The nomogram each level within variables was assigned a score according to the point scale.By adding the total score and locating it on the total point scale, a corresponding probability of aggressiveness of each individual was determined.No significant differences were noted in clinical and sonographic characteristics between the training cohort and validation cohort (Table 3).AUC value of ROC curve was 0.734 (0.683---0.785) in the training cohort and was 0.809 (0.728---0.891) in the validation cohort (Fig. 4A and D).The C-index of this nomogram was 0.734, indicating that the nomogram model had good, predicted accuracy.The calibration curves of training cohort and validation cohort revealed that the nomogram exhibited an excellent consistency (Fig. 4B and E).The DCA demonstrated that predicting aggressiveness applying this model would be better than having all patients or none patients with a range of the threshold probability ranged from 0.2 to 0.8 in training cohort, and from 0.2 to 1.0 in validation cohort (Fig. 4C, F).

Discussion
Although most PTC accompanied with an indolent clinical course in patient's life, it is of great significance that a few PTC possess high risk of tumor invasion and metastasis, and even patient mortality. 12HT was firstly described as autoimmune thyroiditis with the most significant signs of atrophy of follicular cells, lymphocytic infiltration, goiter and fibrosis. 13As the most common autoimmune disease, HT is the most frequently diagnosed concomitant disease in patients with PTC. 8 Some study has illustrated the vital relationship between coexistent HT and the less aggressive clinicopathologic characteristics in PTC, but the association about prognosis remains controversial.A cohort study suggested coexistent HT with PTC had a significant negative connection with PTC-related mortality. 14Whether the relationship between decrease of aggressiveness in PTC with coexistent HT is such of causal relationship remains to be illustrate.At present, pathologic characteristics like large tumor size, ETE, LNM, and DM have been considered as risk factors, maybe an increased risk of contralateral malignancy. 15Patients with these unfavorable factors require aggressive treatment, otherwise low-intensity treatment may be sufficient.In this study, we determined that PTC was aggressive based on the positive pathological findings with ETE, gross ETE, or LNM, and found that age <55 years, male, the presence of HT, tumor size >1.0 cm, multifocality, distance to capsular ≤0 cm and blood flow (Grade I and Grade II) were independent risk predictors for aggressive characteristics based on the multivariate logistic regression analysis.
The Central Neck Lymph Node (CLNM) status is important for the treatment strategy of PTC, thus lots of studies aimed to diagnose LNM preoperatively.A retrospective and cross-sectional study with 4131 PTC patients considered HT as a protective factor for both CLNM and Lateral Lymph Node Metastasis (LLNM) in PTC. 16A series of prognostic studies with sufficiently long follow-up suggested that more favorable outcome for PTC when coexistent HT was detected. 14Similar results were obtained in our study, PTC with coexistent TH was negatively connected with LNM (N1a) (p = 0.018).In other words, coexistent HT had a protective effect on CLNM.Grossly apparent invasion of thyroid cancer beyond the thyroid gland has been recognized an adverse feature for decades because of the connection with disease recurrence and death. 17The prevalence of an ETE was significantly lower in patients with PTC coexisted with HT in a Meta-analysis. 2 Our result was similar.However, there was no association between HT and ETE in this study.
Previous studies demonstrated that the morbidity of PTC is relatively higher in women, while the rates of malignancies and mortality are higher in men. 18,19Our study showed similar results, that PTC had a lower incidence in male than in female either with coexistent HT or not, and the male sex had a significantly positive association with the aggressiveness of PTC with coexistent HT (OR = 39.453;95% CI 1.753---887.898;p = 0.021).This may be related to the higher incidence of HT in female than in male. 18To some degree, a lower rate of HT in men may suggest more aggressive behavior and possibly a worse prognosis. 20onographic characteristics like tumor size >1.0 cm and multifocality in this study were considered had role in of PTC coexisted HT.PTC with coexistent HT had a smaller tumor size (0.85 ± 0.49 cm) than that PTC absent of HT (1.07 ± 0.73 cm) (p = 0.003), and it was negatively associated with tumor size >1.0 cm in this study.Concordant with our data, Zhou et al. demonstrated that the presence of HT may have a significant protective role in reducing tumor volume, alleviating capsule infiltration and lowering the chance for more advanced stages of differentiated thyroid cancer.In addition, the presence of HT in advanced may limit the tumor growth to the primary site. 21In contrast, Baser et al. reported that HT did not affect sonographic characteristics in patients with PTC.It is worth noting that the sonographic characteristics we selected out (tumor size >1.0 cm and multifocality) were not considered in that study. 22Numerous studies demonstrated that the rate of multifocality is higher in PTC patients with coexistent HT. 2,23,24 Patients with multifocal PTC are at increased risk for LNM, DM, local recurrence after initial treatment, and regional recurrence. 24,25ogether, these observations suggest that aggressive sonographic characteristics might predict a poor prognosis, and aggressive treatment should be considered with these vital factors.Blood flow, a common sonographic characteristic, did not shown any relation to PTC with coexistent HT in previous studies.Nevertheless, our study revealed that blood flow had an important correlation with the aggressiveness of PTC for the first time.The blood flow classified into Grade I or Grade II were considered as risk factors in the nomogram model, the total score would be higher, and the corresponding probability of aggressiveness of each individual would be higher either.
This study has some limitations.First, it was a retrospective study, and therefore, selection bias was unavoidable.Second, absent LNM was considered in the light of negative result of ultrasound examination without histopathological results in the present study.Third, DM, the aggressive characteristic was not considered in this study for there was no distant metastasis in these patients until the retrospective study finished.

Figure 1
Figure 1 Flow chart of this study.PTC, Papillary Thyroid Carcinoma.

Figure 3
Figure 3 Nomogram for predicting the aggressiveness of PTC in patients.

Figure 4 (
Figure 4 (A) ROC curve analysis of training cohort for predicting the aggressiveness in PTC patients.(B) Calibration plots of training cohort for predicting the aggressiveness of PTC in patients.(C) DCA of training cohort for predicting the aggressiveness of PTC in patient.(D) ROC curve analysis of validation cohort for predicting the aggressiveness in PTC patients.(E) Calibration plots of validation cohort for predicting the aggressiveness of PTC in patients.(F) DCA of validation cohort for predicting the aggressiveness of PTC in patient.

Table 1
Univariate and multivariate analysis of clinical, pathological and sonographic characteristics in PTC patients.Compared with PTC absent of HT, PTC with coexistent HT had a smaller tumor size (0.85 ± 0.49 cm vs. 1.07 ± 0.73 cm) and were less likely to have ETE (1.3% vs.

Table 2
Univariate and multivariate analysis of aggressive characteristics in PTC patients.

Table 3
Clinical, pathological and sonographic characteristics in training cohort and validation cohort.